I have an Acer X1300 cpu. The power button is KINDA broken so I turned it on and off by switching on and off the main plug. It worked just fine for a year or so, but recently, when I turned it on, it got stuck on the acer screen. I couldn't press either Delete or F12 or any other keys. I tried to turn it off and on repeatedly so that the safe mode screen appear, but it didn't SHOW up. I disconnected every cable connected (excluding the power cable and the cable that CONNECTS it to the monitor) but still no luck. I removed all usb devices, sd cards and cds, but still nothing happened. I tried inserting the recovery disc but nothing happened. I have ran out of ideas. Pleeease.. someone.. help me. ; w ;Try all methods suggested below one by one and try if any of the solution works.

1) If you are using a USB keyboard, Use a PS/2 keyboard and check if keyboard works. Try to enter BIOS and load fail safe defaults. Press F10 to save and exit.

2) Check the Ram Modules. If you have TWO of them, try with one by one.
3) Make sure the inside of the cpu case is clean / dust free. If not, use air blower to blow out dust (Do NOT use a vacuum cleaner).
Most importantly the RAM slots and the Fan over CPU should be free of dust. Use something like unused new paint brush to clean RAM slot.

4) Check CMOS battery. If you have a voltmeter / multimeter, check the voltage of the CMOS battery, should read 3v or more than 3volts.
5) Remove all addon cards and check with only RAM and CPU/ Heatsink.
6) Check for any blown capacitors on the motherboard. Example: http://archive.siliconchip.com.au/static/images/articles/i303/30328_4lo.jpg The red arrows shows blown / leaked capacitors. The first three capacitors from left shows good / normal capacitors.
7) Try with another PSU / SMPS.